Which unit is not equivalent to milliliters?

Milliliters (mL) is a unit of volume in the metric system, specifically used to measure liquids. When considering the options, cc (cubic centimeters) is equivalent to milliliters since 1 cc is equal to 1 mL. Similarly, mL itself is the same as the other option, maintaining equivalence.

The unit mg (milligrams) measures mass rather than volume, representing the weight of a substance. On the other hand, g (grams) is also a unit of mass. Since both mg and g pertain to weight rather than volume, they cannot be considered equivalent to milliliters. Therefore, the identification of mg as the choice that does not represent a volume unit is accurate. This distinction is crucial for understanding measurements in medication administration, where precision in volume and dosage is vital for safe and effective patient care.